oscillator, electronic, electronic circuit that produces an output signal of a specific frequency. An oscillator generally consists of an amplifier having part of its output returned to the input by means of a feedback loop; the necessary and sufficient condition for oscillation is that the signal, in passing from input to output and back to input via the feedback loop, arrive at the input with no change in amplitude or phase. If this condition is met for only a single frequency, the output is a pure sine wave; if it is met for more than one frequency, the output is a complex wave. Some oscillators are designed to operate under certain conditions so that the output is a square wave, a triangular wave, or a pulse. In some cases, a very stable mechanical oscillator, such as a specially prepared quartz crystal, may be coupled to an electronic oscillator to enhance its frequency stability. The frequency of a voltage-controlled oscillator, used in frequency modulation, is automatically adjusted by a small control current.

electronic music or electro-acoustic music, term for compositions that utilize the capacities of electronic media for creating and altering sounds.

Initially, a distinction must be made between the technological development of electronic instruments and the music conceived to utilize the inherent advantages of these instruments. Experiments in electronic tone production began soon after the invention of the vacuum tube (see electron tube). The first important instrument, the theremin, invented by the Russian Leon Theremin in 1920, used interference beats of two oscillators to produce sine-wave tones. The Ondes Martinot, invented in 1928, and the Trautonium, invented in 1930, were of similar design.

The earliest pieces of electronic music used recorded sounds that were then electronically altered to create sonic collages. This style, called musique concrete, was developed in Paris in 1948 by Pierre Schaeffer. The invention of the tape recorder in the late 1940s gave composers new means for modifying recorded sounds, including splicing (cutting the tape to create new juxtapositions of sound), speed variation (which changes the pitch of the recorded sound), and mixing (which allowed two or more different recordings to be played back at the same time). In popular music, Les Paul was one of the pioneers of electronic music, inventing the first solid-body electric guitar in 1946 and recording music in the 1950s in an eight-track recording studio of his own design.

Controlling aspects of the musical sound by means of voltage regulation eventually led to the invention of synthesizers, devices that could produce and modify sound for musical applications. Among the earliest of these was the RCA synthesizer developed in the late 1950s and used extensively by composer Milton Babbitt in many of his electronic works. In the 1950s various studios that specialized in the production of electro-acoustic music were developed, including the West German Radio Studio in Cologne, associated with composer Karlheinz Stockhausen, the Italian Radio Studio in Milan, associated with Luciano Berio and Bruno Maderna, and the Columbia-Princeton Electronic Music Center, associated with Otto Luening, Vladimir Ussachevsky, Mario Davidovsky, and Babbitt.

During the 1960s synthesizers were made widely available by companies such as Moog and Buchla and found widespread usage in rock music. Popular groups such as the Beatles and the Beach Boys began experiments in multitrack recording, years after the innovations of Paul, that enabled several different recordings to be synchronized on the same tape. Eventually synthesizers switched from voltage control to digital control.

In 1983 the MIDI (Musical Instrument Digital Interface) standard was agreed on by synthesizer manufacturers (see computer music). This digital code enables different electronic devices to communicate a variety of information to each other and allows computer control of synthesizer output. MIDI can also be used to control a wide range of equipment in addition to synthesizers; these include mixers, lights, and signal processors (devices that modify sounds by adding reverberation, by modifying pitch, and by other means).

Today MIDI is widely used in both academic and popular musical production. In MIDI production, computers are often used as sequencers (devices that control the output of musical instruments and signal processors). Throughout the last three decades of the 20th cent. electronic music increasingly became a part of pop music compositions, eventually allowing a solo artist to compose, produce, and perform music that employs a full complement of instrumental sounds. In the 1980s MIDI was also used in the creation of the radio baton, a new instrument that allows players to control the nuances of the music played.

electronic mail or e-mail, the electronic transmission of messages, letters, and documents. In its broadest sense electronic mail includes point-to-point services such as telegraph and facsimile (fax) systems. It is commonly thought of, however, in terms of computer-based message systems where the electronic text file that is received can be edited, replied to, excerpted, or even pasted into another electronic document that can be used or manipulated by a word processor, desktop publishing system, or other computer program. Users of such systems, called store-and-forward or mailbox systems, can broadcast messages to multiple recipients, read and discard messages, file and retrieve messages, or forward messages to other users. Extensions to e-mail allow the user to add graphics and sound to messages, and files can be attached to e-mails. Computer-based messaging can take place on a single computer, a computer network, or across gateways linking different computer networks (as through the Internet). With the increasing use of e-mail, unsolicited commercial e-mail, known as spam, has become a significant problem. E-mail, especially through attachments, has also become a means for disseminating computer viruses and other malicious programs.

electronic game, device or computer program that provides entertainment by challenging a person's eye-hand coordination or mental abilities. Made possible by the development of the microprocessor, electronic games are marketed in various formats, such as hand-held one-player models, cartridges or compact discs that are inserted in modules attached to television sets, computer programs run on personal or network computers, and freestanding arcade versions. Most of their appeal comes from the computer program that synchronizes flashing lights and a variety of sounds with the movielike animated action portrayed on a graphic display (see computer graphics). As the technology has advanced from 8-bit microprocessors to ever faster chips with greater graphic and sound capabilities, the programming has kept pace. For example, the newest games have so many levels and twists that they may take more than 100 hours to complete, and the graphic capabilities allow the game player to alter the visual perspective from narrow to panoramic. The games may be contested among several players, or an individual may engage in a test of skill against the computer. Some Internet-based games, known as massively multiplayer on-line games (MMOGs), involve thousands of individuals interacting with each other in ongoing, open-ended play; by 2007 MMOGs were a $1 billion industry. Game subjects include sports (e.g., baseball and football); action warfare, adventure, and role-playing; casino gambling (e.g., as roulette, poker, and simulated slot machines); and such classics as solitaire, contract bridge, chess, and backgammon. See also virtual reality.

electronic engineering: see engineering.

Any music involving electronic processing (e.g., recording and editing on tape) and whose reproduction involves the use of loudspeakers. In the late 1940s, magnetic tape began to be used, especially in France, to modify natural sounds (playing them backward, at different speeds, etc.), creating the genre known as musique concrète. By the early 1950s, composers in Germany and the U.S. were employing assembled conglomerations of oscillators, filters, and other equipment to produce entirely new sounds. The development of voltage-controlled oscillators and filters led, in the 1950s, to the first synthesizers, which effectively standardized the assemblages and made them more flexible. No longer relying on tape editing, electronic music could now be created in real time. Since their advent in the late 1970s, personal computers have been used to control the synthesizers. Digital sampling—composing with music and sounds electronically extracted from other recordings—has largely replaced the use of oscillators as a sound source.

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in full electronic mail

Messages and other data exchanged between individuals using computers in a network. An e-mail system allows computer users to send text, graphics, and sometimes sounds and animated images to other users. It developed from large organizations using an internal messaging system as a communication link among employees. The mass provision of e-mail addresses for private individuals by Internet service providers led to the development of e-mail as a system to supplement or replace communication by letter.

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Collection of data or information organized for rapid search and retrieval, especially by a computer. Databases are structured to facilitate storage, retrieval, modification, and deletion of data in conjunction with various data-processing operations. A database consists of a file or set of files that can be broken down into records, each of which consists of one or more fields. Fields are the basic units of data storage. Users retrieve database information primarily through queries. Using keywords and sorting commands, users can rapidly search, rearrange, group, and select the field in many records to retrieve or create reports on particular aggregates of data according to the rules of the database management system being used.

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Communication between parties at a distance from one another. Modern telecommunication systems—capable of transmitting telephone, fax, data, radio, or television signals—can transmit large volumes of information over long distances. Digital transmission is employed in order to achieve high reliability with minimal noise, or interference, and because it can transmit any signal type, digital or analog. For digital transmission, analog signals must be subjected to a process of analog-to-digital conversion; most television, radio, and voice communications are analog and must be digitized before transmission. Transmission may occur over cables, wireless radio relay systems, or via satellite links.

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United Nations agency headquartered in Geneva. Its roots can be traced to 1865, when the International Telegraph Union was established to coordinate international development of the telegraph. It acquired its present name in 1934 and became a UN specialized agency in 1947. Its activities include regulating allocation of radio frequencies, setting standards on technical and operational matters, and assisting countries in developing their own telecommunications systems.

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in full electronic commerce

business-to-consumer and business-to-business commerce conducted by way of the Internet or other electronic networks. E-commerce originated in a standard for the exchange of documents during the 1948–49 Berlin blockade and airlift. Various industries elaborated upon the system until the first general standard was published in 1975. The electronic data interchange (EDI) standard is unambiguous, independent of any particular machine, and flexible enough to handle most simple electronic transactions. In addition to standard forms for business-to-business transactions, e-commerce encompasses much wider activity—for example, the deployment of secure private networks (intranets) for sharing information within a company, as well as selective extensions of a company's intranet to collaborating business networks (extranets). A new form of cooperation known as a virtual company, actually a network of firms, each performing some of the processes needed to manufacture a product or deliver a service, has flourished.

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